Plate data: Bird (2003), PB2002, converted by Hugo Ahlenius, Nordpil (ODC-By 1.0). Land: Natural Earth (India POV).
The Australian Plate carries Australia, New Guinea and the seafloor between the Indian and Pacific Oceans. Older maps often join it with the Indian Plate as one Indo-Australian Plate. PB2002 treats them as two plates, with their own boundary in the Indian Ocean.
Bird (2003) notes that there are fast and significant motions between the India and Australia plates, so PB2002 keeps them apart. He also cites work by Royer and Gordon (1997) showing, with high confidence, that the Australian Plate is not rigid. They proposed a separate Capricorn plate inside it, diverging from Australia by about 1.2 mm per year in the southwest and converging by about 2.1 mm per year in the northeast. Bird did not add it to PB2002: those rates do not differ from zero with 95% confidence, and with no islands on the proposed plate there is little chance of new geodetic data.
Its northern and eastern edges are crowded with small plates in PB2002, from the Banda Sea and Timor to Tonga and the New Hebrides, which is why its neighbor list below is long. Many of these edges are convergent, as the table below shows.1 In the southeast, back-arc spreading in the Havre Trough continues into the Taupo volcanic zone on the North Island of New Zealand. Bird adds a small Kermadec Plate east of it, named after the island chain along its center (Bird 2003).
The continent itself has travelled a long way. USGS describes dinosaur fossils from Dinosaur Cove, at the southeastern tip of mainland Australia, of species that seem well adapted to cold. When they lived, their habitat lay well within the Antarctic Circle, evidence that Australia has drifted north toward the equator during the past 100 million years (USGS). About 225 million years ago, India was still a large island off the Australian coast (USGS).
Australian Plate in numbers
Measured from its PB2002 outline, the Australian Plate covers about 46.0 million km², or 9% of the
Earth's surface. That makes it number 6 by area of the 52 plates in the model.
It spans from 63°S to 2°N and from 65°E to 176°W.
Its edge is about 36,901 km long, mostly divergent:
42.1%divergentDivergent boundary. Plates pull away from each other and new crust forms between them. Source (15,542 km)
, 30.7%convergentConvergent boundary. Plates move toward each other and crust is destroyed as one plate dives under another. Source (11,337 km)
and 27.2%transformTransform boundary. Plates slide horizontally past each other. Crust is neither made nor destroyed. Source (10,022 km)
.
Countries whose main landmass sits on this plate: Australia, Fiji, New Caledonia, New Zealand and Papua New Guinea. Countries that straddle a boundary
are listed under the plate that holds the center of their largest landmass.
Australian Plate fact table
Australian Plate at a glance, computed from PB2002
Along its boundaries it moves a mean 4.9 cm/yr relative to its neighbors, fastest against the New Hebrides Plate. Bird (2003)
Neighboring plates Neighbors. Plates that share a boundary with this plate. Most plate movement happens along these narrow zones between plates. Source
The Australian Plate shares a boundary with 18 plates in PB2002, longest shared edge first.
The longest, about 11,155 km, is with the Antarctic Plate; the shortest, about 132 km, is with the Birds Head Plate.
